Phylogenetic analysis and characterization of Korean orf virus from dairy goats: case report

Rapid Onsite Visual Detection of Orf Virus Using a Recombinase-Aided Amplification Assay

Orf is an important zoonotic disease caused by the Orf virus (ORFV) which can cause contagious pustular dermatitis in goats and sheep. Orf is widespread in most sheep-raising countries in the world, causing huge economic losses. Although diagnostic methods for ORFV infection already exist, it is still necessary to develop a time-saving, labor-saving, specific, low-cost and visual diagnostic method for rapid detection of ORFV in the field and application in grassroots laboratories. This study establishes a DNA extraction-free, real-time, visual recombinase-aided amplification (RAA) method for the rapid detection of ORFV. This method is specific to ORFV and does not cross-react with other common DNA viruses. The detection limits of the real-time RAA and visual judgment of the RAA assay at 95% probability were 13 and 21 copies per reaction for ORFV, respectively. Compared with qPCR, the sensitivity and specificity of the real-time RAA assay were 100%, and those of the visual RAA assay were 92.31% and 100.0%, respectively. The DNA extraction-free visual detection method of RAA established in this study can meet the needs of rapid onsite detection and grassroots laboratories and has important reference value and significance for the early diagnosis of diseased animals.

Identification, molecular characterization, and pathological features of orf virus in sheep and goats in Punjab province, Pakistan

Orf virus (ORFV) causes an acute, contagious, skin disease of sheep and goats which is economically important. The objectives of this study were to identify ORFV and to explore its pathological and phylogenetic profiles in 350 goats and 91 sheep of 14 districts of Punjab, Pakistan, from July 2020 to July 2021. Skin scrapings (total no. of samples = 441) of suspected animals were subjected to polymerase chain reactions, phylogenetic analysis, and pathological observations. The partial length of GIF/IL-2 gene (408 bp) was successfully amplified in 58/441 samples. Phylogenetic analysis of GIF/IL2 gene showed that the study isolates belonged to ORFV-cluster I, together with the viruses reported in India and China. Pakistan ORFV isolates were shared 97.6-98.7% nucleotide and 97.6-100% amino acid identities with the reference strain (NC_005336). Moreover, Chinese ORFV-isolates were detected unique multiple amino acid substitutions (F11L, Q21H, D27N, I46V, N49S, N82D, D103N, S129G) with study isolates. Naturally infected animals were anorexic, emaciated, dull, and depressed. The macroscopic lesions included multifocal to coalescing, ulceration followed by proliferative papules, pustules, and crust formation on the epidermis of gums, lips, mouth commissure, muzzles, nose, and udder. Histopathological examination revealed hyperplasia, anastomosing rete ridges formation and degenerative changes, including spongiosis and vacuolation of epidermal cells. Keratinocytes exhibited eosinophilic intracytoplasmic inclusion bodies with pyknotic and karyorrhexis nuclei. This is the first report on molecular characterization of ORFV from Pakistan, with insight into its pathogenesis and comparative analysis of pathological alterations and genetic diversity between ORFV strains reported in different geographical areas.

Molecular phylogenetic analysis of bovine papular stomatitis viruses detected in Saga, Japan

In this study, we performed a molecular phylogenetic analysis of six bovine papular stomatitis virus (BPSV) field strains detected from Japanese beef calves kept on a farm in Saga prefecture, a southwest part of Japan, from 2017 to 2020. The phylogenetic analysis based on a partial B2L gene (554-nt) showed that these field strains were divided into two lineages, a lineage (A-lineage) constructed by a Saga strain and strains obtained from various regions of Japan and the world, and other lineage (B-lineage) constructed by five Saga strains and strains obtained from France, USA and Iwate prefecture (a north part of Japan). Furthermore, a Saga field strain named BPSV_SAGAbv2 and strains obtained from USA and Iwate prefecture belonged to a sub-lineage blanched from B-lineage. This is the first report elucidating molecular epidemiological characters of field BPSVs obtained from Saga prefecture. The existence of the multiple lineages was thought to be related to a history of calf introduction from various regions of Japan into Saga prefecture.

Contagious ecthyma: how serious is the disease worldwide?

Contagious ecthyma (CE) is an infectious disease of small ruminants caused by a parapoxvirus of family Poxviridae subfamily Chordopoxvirinae. The disease is obviously distinguished by an establishment of scabby lesions and ulcerative formation on less hairy areas including muzzle, ears, nostril, and sometimes on genitalia. The disease is endemic in sheep and goats. The virus is transmissible to other ruminants and is a public health concern in humans. Although the disease is known as self-limiting, it may cause a significant economic threat and financial losses due to lower productivity in livestock production. Information with regard to the risk of the disease and epidemiology in most parts of the world is underreported. This paper aims to provide relevant information about the epidemiology of CE in selected regions of Europe, South America, North America, Asia, Africa, and Australia. An in-depth comprehension of virus infection, diagnoses, and management of the disease will enable farmers, researchers, veterinarians, abattoir workers, health personnel, and border controllers to improve their measures, skills, and effectiveness toward disease prevention and control, toward reducing unnecessary economic loss among farmers. A herd health program for significant improvement in management and productivity of livestock demands a well planned extension program that ought to encourage farmers to equip themselves with adequate skills for animal healthcare.

Comparative analysis of B2L genes in vaccine and wild strains of orf virus in China

Orf is highly contagious zoonoses which is caused by the orf virus (ORFV). In order to determine the characteristics of B2L genes between vaccine strain and wild strain of ORFV in China. In this study we choose the weak vaccine of ORFV produced in biological products (Shandong Taifeng, China) and the wild strain (FJ-PN) isolated and identified in our laboratory to amplify, clone and sequence the B2L genes, and the changes in nucleotide, amino acid and secondary and tertiary protein structure of the B2L proteins were compared and analyzed by bioinformatics software. Comparison results showed that the nucleotide sequence similarity and amino acid sequence similarity of the B2L genes of vaccine strain and wild strain were 98.6% and 98.7% respectively. There was no significant difference between the primary, secondary and tertiary structures of the B2L proteins. The results of this study provide ideas for the study on the function and molecular biological characteristics of related proteins after the ORFV is weakened.

Development of a recombinase-aided amplification assay for detection of orf virus

Orf, caused by orf virus (ORFV), is an important zoonotic disease that infects goat and sheep, leading to huge economic losses. ORFV can also cause cutaneous lesions in people who come in close contact with the diseased animals. Although accurate diagnostic methods for ORFV infection exist, there is a need for a rapid, specific, and sensitive method for easy clinical application. Here, we successfully established a recombinase-aided amplification (RAA) assay for rapid detection of ORFV. The analytical sensitivity of the assay for ORFV detection is 1 × 10¹ copies per reaction. Moreover, no cross-reaction was observed with other common DNA viruses. A total of 45 archived suspected ORFV infected nasal scab skin samples were examined by RAA and SYBR Green-based real-time polymerase chain reaction (PCR). Compared with the real-time PCR assay, the kappa values of the RAA assay for ORFV detection was 0.845 (p <0.001), indicating that both assay results were fully in agreement. In conclusion, this detection assay provides a rapid, sensitive, and specific method for ORFV detection and is suitable for ORFV clinical testing.

Orf Virus VIR Antagonizes p53-Mediated Antiviral Effects to Facilitate Viral Replication

As a zoonotic disease, ovine contagious pustular dermatitis (Orf) is a serious threat to sheep as well as humans. Orf virus (ORFV) interferon resistance protein (VIR) is the principal virulence protein that encodes a dsRNA-binding protein to inhibit host antiviral response. p53 is one of the key proteins of the host antiviral innate immunity. It not only enhances type I interferon secretion but also induces apoptosis in infected cells, and plays a crucial role in the immune response against various viral infections. However, it remains to be elucidated what role p53 plays in ORFV replication and whether ORFV's own protein VIR regulates p53 expression to promote self-replication. In this study, we showed that p53 has an antiviral effect on ORFV and can inhibit ORFV replication. In addition, ORFV nonstructural protein VIR interacts with p53 and degrades p53, which inhibits p53-mediated positive regulation of downstream antiviral genes. This study provides new insight into the immune evasion mediated by ORFV and identifies VIR as an antagonistic factor for ORFV to evade the antiviral response.

Field investigation and phylogenetic characterization of orf virus (ORFV) circulating in small ruminants and Pseudocowpoxvirus (PCPV) in dromedary camels of eastern Sudan

In this study, livestock herders in eastern Sudan were interviewed through structured questionnaire involved 14046 animals in 151 herds (87 camel herds, 51 sheep and 13 goats) from June to September of 2016 in Showak area of Gadarif State to get some epidemiological information on contagious ecthyma (CE) infection. 102 suspected cases of CE were investigated (38 sheep, 22 goats and 42 camels) by a second questionnaire focusing on age and sex of affected animals beside number and localization of the lesions. Representative tissue samples of scab lesion scrapings were collected from a total of 36 suspected sheep, goats and camels for DNA extraction to identify PPV by quantitative real-time PCR and gel-based PCR, then a PCR protocol was used to obtain DNA fragment of B2L gene from six DNAs (2 from each animal species) for sequencing. Phylogenetic tree based on nucleotide sequences was constructed and all data were analyzed statistically. Obtained result has shown morbidity rate of 23.8% and a case fatality rate of 4.7 % in overall investigated animals resulting in a significant economic loss. Within individual herd, the morbidity rate varied from 5.6 to 42.8%, while the case fatality rate ranged between 0 and 33.3%. Camels accounted for the highest case fatality rate with 6.5% compared to sheep and goats which their rates were 2.8% and 1.3%, respectively. 93% of the affected animals were young less than one-year-old. The prevalence of CE was high in the rainy season compared to winter and summer. Out of 36 scab materials collected from sheep, goats, and camels, 24 gave positive specific amplification in real-time PCR and 21 in the gel-based PCR. DNA sequencing confirmed the PCR results. All sequences had a high G + C content of 62.6-63.9%. A BLAST search also revealed that the studied sheep PPV (SPPV) isolates shared 99.08% nucleotide sequence intragroup identity, 96.88-97.27% identity with the goat PPV (GPPV) isolates and together they belong to the Orf virus (ORFV) species, while the camel PPV (CPPV) isolates are close to the Pseudocowpoxvirus (PCPV) species of the PPV genus and share 92.51-93.62 % identity with the GPPV isolates. In conclusion the present study demonstrated that the gross lesion produced by PPV in sheep, goats and camels is generally similar, yet the PPVs circulating in eastern Sudan in camels (PCPV) are genetically distinct from those affecting sheep and goats (ORFV). Contagious ecthyma in eastern Sudan causes significant morbidities and mortalities and control measures, guided by the results of this investigation ought to be implemented.

Identification of strain diversity and phylogenetic analysis based on two major essential proteins of Orf viruses isolated from several clinical cases reported in Malaysia

There is a little information on the characterization of Orf virus strains that are endemic in Malaysia. The relationship between the severity of disease and the molecular genetic profile of Orf virus strains has not been fully elucidated. This study documented the first confirmed report of contagious ecthyma causing by Orf virus in goats from a selected state of eastern peninsular Malaysia. The disease causes significant debilitation due to the inability of affected animals to suckle which brings a great economic loss to the farmers. A total of 504 animals were examined individually to recognize the affected animals with Orf lesion. Skin scrapping was used to collect the scab material from the infected animals. The presence of Orf virus was confirmed by combination of methods including virus isolation on vero cells, identification by Transmission Electron Microscopy (TEM) and molecular technique using PCR and Sanger sequencing. The results showed the successful isolation of four Orf virus strains with a typical cytopathic effects on the cultured vero cells line. The morphology was confirmed to be Orf virus with a distinctive ovoid and criss cross structure. The phylogenetic analysis revealed that these isolated strains were closely related to each other and to other previously isolated Malaysian orf viruses. In addition these Orf virus strains were closely related to Orf viruses from China and India. This study provides more valuable insight in terms of genotype of Orf virus circulating in Malaysia.

Phylogenetic analysis of Orf virus associated with contagious ecthyma (orf) outbreak in Tellicherry goats (Capra hircus)

Orf virus (ORFV) is a member of genus Parapoxvirus that causes contagious ecthyma in goats. A pox-like disease was investigated in Tellicherry goats (31 female) maintained at a semi-organized farm. History revealed recent introduction of Tellicherry goats for breeding purpose and housing of the new entrants in to a farm already having a mild form of pox-like disease. Newly introduced and stressed Tellicherry goats developed severe form of infection with 100% morbidity. Affected goats showed lesions around lips (100%), commissure (53%) and oral cavity (65%); exanthematic dermatitis was evident in 94% of the affected goats followed by ulceration (47%) and nodular lesions (24%). Scab samples were collected from affected goats to confirm the clinical diagnosis. Genus Parapoxvirus was confirmed by the amplification of specific 594 bp and 235 bp amplicons. Further, Orf virus specific amplicon of size 1,206 bp was also amplified for the confirmation. Sequence analysis of PCR amplicons showed close resemblance of the outbreak strain with reported Indian Orf virus isolates. Based on the homology of the outer envelope protein B2L gene sequence of Orf virus, the source of infection to the Tellicherry goats was traced to the local goat. Although Orf virus is zoonotic; however, no occupational transmission was noticed in the present outbreak.

Development of a SYBR Green I real-time PCR for the detection of the orf virus

Orf is a non-systemic, ubiquitous disease of sheep and goats caused by the orf virus (ORFV). ORFV occasionally causes cutaneous lesions in humans in contact with infected animals. In the present study, a real-time PCR method was established for detection of ORFV using the fluorescent chimeric dye SYBR Green I. Specific primers were designed to target a highly conserved region of the ORFV B2L gene. This method was able to detect a minimum of 20 copies of ORFV genomic DNA. The results showed no cross-reactions with other common DNA viruses. The time required for the test was approximately 1.5 h. Clinical test samples showed that this method was faster and had a higher sensitivity than traditional PCR. In conclusion, this novel, real-time PCR-based assay provides a rapid, sensitive, and specific method for ORFV detection. This test provides improved technical support for studies regarding the clinical diagnosis and epidemiology of ORFV.

Molecular characterization of Orf virus in goats in Gabon, Central Africa

BACKGROUND

Orf or contagious ecthyma is a zoonotic viral infection with a potential serious health threat for the small ruminants industry as well as humans. It is currently emerging in new territories.

RESULTS

Eight suspected clinical cases of pustular dermatitis in goats occurred in the rural area of Tebe, in south-eastern Gabon, in January 2013. The orf virus (ORFV) was detected by high-throughput sequencing on sera, buccal swabs and scab pool samples. It was confirmed in six out of eight sick goats by using specific PCR targeting the major envelope protein (B2L) and the orf virus interferon resistance (VIR) genes. Phylogenetic analysis revealed that the Gabonese strain and South Korean strains evolved from a common ancestor, suggesting an Asian origin of the ORFV' Gabonese strain.

CONCLUSIONS

This study provides the molecular detection of the ORFV strain involved in the cases of pustular dermatitis in goats and highlights its circulation in Gabon.

Molecular characterization of orf virus from sheep and goats in Ethiopia, 2008-2013

Background

Orf is a contagious disease of sheep, goats and wild ungulates caused by orf virus (ORFV) a member of the genus Parapoxvirus, Poxviridae family. Although orf is endemic in Ethiopia, little attention has been given so far as it is not a notifiable disease by the World Organization for Animal Health. In this work, we have investigated orf outbreaks representing five different geographical locations of Ethiopia, in Amba Giorgis, Gondar zuria, Adet, Debre zeit and Adami Tulu, between 2008 and 2013.

Results

The viral isolation and the sequence analysis of the A32L and the B2L genes of eighteen representative isolates confirmed that sampled animals were infected by ORFVs.

The phylogenetic study and the comparative analysis of the deduced amino acid profile suggests that there were two main clusters of ORFV isolates which were responsible for the investigated outbreaks. Additionally the analysis of these two genes showed limited variability to ORFVs encountered elsewhere. This is the first report on the genetic characterization of the ORFV isolates from sheep and goats in Ethiopia.

Conclusion

The molecular characterization of Ethiopian ORFV isolates highlighted the circulation of two main clusters causing orf disease in sheep and goats. The use of laboratory based methods and a constant monitoring of Ethiopian ORFV isolates is needed to better understand the dynamic of ORFV circulating in the country and facilitate the implementation of control measures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0489-3) contains supplementary material, which is available to authorized users.

Phylogenetic analysis of three orf virus strains isolated from different districts in Shandong Province, East China

Orf virus (ORFV) is the causative agent of contagious ecthyma, which is a zoonotic disease that affects sheep, goats, wild small ruminants and humans. Shandong Province in East China is one of the main producing areas in China for sheep and goats. Here, we conducted epidemiological surveys in different areas in this Province, isolated three orf virus strains, SDLC, SDTA and SDJN, from goat flocks and then analyzed the genetic evolution of these strains. The ORFV011, ORFV059, ORFV109, ORFV110 and ORFV127 genes of these three strains were amplified, sequenced and analyzed. Phylogenetic analysis showed that ORFV011 of the SDLC and SDTA strains cluster together with the Gansu, Liaoning, Shanxi, Nantou, Hoping and FJ-YX strains, while SDJN clusters with the FJ-GS and FJ-GO strains. ORFV059 of the SDLC and SDTA strains cluster together with the FJ-YX strain, while SDJN clusters with the FJ-GS and FJ-GO strains. ORFV059 and ORFV127 of these three strains were similar to those of the OV-SA00 strain. The results suggested that SDLC, SDTA and SDJN originated from Fujian Province and formed a complex group of viruses in Shandong Province. As the role of ORFV127 gene responsible for the immune evasion of ORFV, the pathogenesis of these three virus strains may similar to that of OV-SA00. These three strains first isolated in Shandong Province are novel ORFV strains, and the data reported here will be helpful for further research about ORFV and its comprehensive prevention and control.

Orf virus infection in sheep or goats

Orf virus, a member of the genus Parapoxvirus, is the causative agent of contagious ecthyma ('Orf'). It is a pathogen with worldwide distribution, causing significant financial losses in livestock production. The disease mainly affects sheep and goats, but various other ruminants and mammals have been reported to be infected as well. It is also a zoonotic disease, affecting mainly people who come in direct or indirect contact with infected animals (e.g. farmers, veterinarians). The disease is usually benign and self-limiting, although in many cases, especially in young animals, it can be persistent and even fatal. Production losses caused by Orf virus are believed to be underestimated, as it is not a notifiable disease. This review of literature presents all latest information regarding the virus; considerations regarding treatment and prevention will be also discussed.

Phylogenetic analysis of B2L gene of Egyptian orf virus from naturally infected sheep

Orf is a viral disease caused by a parapoxvirus, affecting primarily sheep and goats and causes severe economic losses. In this study, a total of 500 sheep from a farm in El-Beheira Governorate, Egypt were examined during spring, 2014. Out of them, 30 sheep showed clinical signs of orf virus infection. The diseased sheep exhibited proliferative lesions on the lips and around the mouth. Polymerase chain reaction (PCR) was used for diagnosis of the disease. For genetic characterization of the Egyptian orf virus, the sequence of a major and highly immunogenic envelope protein gene (B2L gene) was identified and compared with the sequences available from different parts of the world. The virus was detected in 24 out of 30 collected samples (80 %) by PCR. Phylogenetic analyses of the Egyptian orf virus B2L gene showed close genetic relationship with Israel orf viruses those were identified in 2012. In conclusion, this study reports identification and genetic characterization of Egyptian orf virus in sheep in Egypt.

Identification, phylogenetic evolutionary analysis of GDQY orf virus isolated from Qingyuan City, Guangdong Province, southern China

Infection with the orf virus (ORFV) leads to contagious ecthyma, also called contagious pustular dermatitis, which usually affects sheep, goats and other small ruminants. It has a great distribution throughout the world and has also been reported to infect humans. Though many strains have been isolated from differing parts of mainland China, rarely has any strain been reported from the southern provinces of China. We studied a case of orf virus infection that occurred at Qingyuan City, Guangdong Province in southern China. An orf virus strain, GDQY, was successfully isolated and identified through cell culture techniques and transmission electron microscopy. Complete genes of ORFV011, ORFV059, ORFV106 and ORFV107 were amplified for the sequence analysis based on their nucleotide or amino acid level. In order to discuss the genetic variation, precise sequences were used to compare to other reference strains isolated from different districts or countries. Phylogenetic trees based on those strains were built up and evolutionary distances were calculated based on the alignment of their complete sequences. The typical structure of the orf virus was observed in cell-culture suspensions inoculated with GDQY, and the full-length of four genes was amplified and sequenced. Phylogenetic analysis indicated that GDQY is homologous to FJ-DS and CQ/WZ on ORFV011 nucleotides. ORFV059 may be more variable than ORFV011 based on the comparison between GDQY and other isolates. Genetic studies of ORFV106 and 107 are reported for the first time in the presented study.

Comparative genomic sequence analysis of Chinese orf virus strain NA1/11 with other parapoxviruses

Orf virus (ORFV) is a typical member of the genus Parapoxvirus. The parapoxvirus genome consists of highly variable terminal regions and relatively conserved central regions with a high G + C content. In our previous study, a novel ORFV strain, NA1/11, was isolated from northeastern China. To fully characterize this strain, we sequenced the entire genome of NA1/11 and conducted a comparative analysis using multiple parapoxviruses. The genomic sequence of NA1/11 was found to consist of 137,080 nucleotides with a G + C content of 63.6 %, but it did not contain the terminal hairpin sequence. Alignment of ORFs from NA1/11 with NZ2, IA82 and SA00 revealed several highly variable ORFs, while the most evident ones are ORFs 001, 103, 109-110, 116 and 132. An odd phenomenon in the region of ORFs 118-120 is that the non-coding fragments are almost as long as the coding fragments. By comparative analysis of inverted terminal repeats, we identified one repeat motif and a long conserved fragment. By comparing the ITRs of SA00 with those of three other ORFVs, more clues were obtained about the correlation between ITR sequence and host adaption. Comparison of the NA1/11 genome with the sequences of other strains of ORFV revealed highly variable regions, thus providing new insights into the genetic diversity of ORFV.

Human infection with ORF virus from goats in China, 2012

Orf virus, which belongs to the Parapoxvirus genus, induces a zoonotic infectious disease characterized by acute, highly vascularized cutaneous pustular lesions in sheep and goats. A number of Orf outbreaks have been reported in sheep and goats in recent years, but no reports have described an Orf virus strain from humans in China. In this study, we diagnosed Orf virus infection in two people, a mother and son, in the Gansu province of China. The human Orf virus was isolated and its phylogenetic characterization was analyzed based on a complete B2L gene. The results are useful for developing prospective programs to control Orf virus infections in both goats and humans.

Comparison and phylogenetic analysis based on the B2L gene of orf virus from goats and sheep in China during 2009-2011

As a zoonotic infectious disease, orf outbreaks have been reported in China in recent years. However, molecular epidemiology analysis has not been performed for Chinese orf virus (ORFV) strains. Here, we have identified 13 ORFVs from goats and sheep in China between 2009 and 2011. Thirty-four complete B2L sequences were used to construct a phylogenetic tree to elucidate the molecular epidemiology of ORFV in China. Nucleotide sequences of B2L genes of clinical samples and attenuated vaccine strains were aligned and compared. Three genotypes were found by molecular epidemiology analysis. Amino acid substitutions were dispersed among B2 polypeptides from wild and attenuated ORFV strains.

Isolation and characterization of orf viruses from Korean black goats

Five cases of orf virus infection in Korean black goats were diagnosed in our laboratory between 2010 and 2011. One orf virus (ORF/2011) was isolated from an ovine testis cell line (OA3.Ts) for use as a vaccine candidate. Sequences of the major envelope protein and orf virus interferon resistance genes were determined and compared with published reference sequences. Phylogenetic analyses revealed that orf viruses from Korean black goats were most closely related to an isolate (ORF/09/Korea) from dairy goats in Korea. This result indicates that the orf viruses might have been introduced from dairy goats into the Korean black goat population.

Bovine papular stomatitis virus (BPSV) infections in Korean native cattle

An outbreak of a disease with parapox-like symptoms was reported in South Korea in April 2012. Three of 45 Korean native cattle, age 20-24 months, were affected. Parapoxviruses were detected and identified by electron microscopy and polymerase chain reaction (PCR). To determine the genetic characteristics of the Korean strains, the sequence of the major envelope protein (B2L) was determined and compared with published reference sequences. Phylogenetic analysis revealed that the parapoxvirus strains were closely related to not only isolates from Japan, but also isolates from Germany, Sudan and the United states. This is the first report on an outbreak and the molecular characterization of BPSV in Korea.

Isolation and phylogenetic analysis of orf virus from the sheep herd outbreak in northeast China

BACKGROUND

Orf is a zoonotic and epitheliotrophic contagious disease that mainly affects sheep, goats, wild ruminants, and humans with a worldwide distribution. To date, there is little information on the characterization of ORFV strains that are endemic in Mainland China. In addition, the relationship between the severity of disease and the molecular profile of ORFV strains has not been fully elucidated.

RESULTS

From the recent outbreak of a sheep herd in Nongan, northeast of China, the novel orf virus (ORFV) strain NA1/11 was successfully isolated. Western blot analysis indicated that the NA1/11 strain cross reacts with monoclonal antibody A3 and infected sheep ORFV antiserum. The purified virions revealed the typical ovoid shape when observed by atomic force microscopy. To determine the genetic characteristics of the NA1/11 strain, the sequences of ORFV011 (B2L), ORFV059 (F1L), ORFV109, ORFV110 and ORFv132 (VEGF) genes were amplified and compared with reference parapoxvirus strains. Non-metric multidimensional scaling (nMDS) was performed to analyze the nucleotide similarities between different ORFV strains.

CONCLUSIONS

Phylogenetic analysis based on ORFV 011 nucleotide sequences showed that the NA1/11strain was closely related to Xinjiang and Gansu strains. ORFV110 and ORFV132 genes are highly variable. The results revealed that precise phylogenetic analysis might provide evidence for genetic variation and movement of circulating ORFV strains in Northeast China. In addition, nMDS analysis showed that geographic isolation and animal host are likely major factors resulting in genetic differences between ORFV strains.

Phylogenetic analysis of strains of Orf virus isolated from two outbreaks of the disease in sheep in Greece

Background

Although orf is endemic around the world, there are few descriptions of Orf virus strains and comparisons of these strains. We report the sequence and phylogenetic analysis of the partial B2L gene of Orf virus from two outbreaks of the disease in Greece. The first was an outbreak of genital form of the disease in a flock imported from France, whilst the second was an outbreak of the disease in the udder skin of ewes and around the mouth of lambs in an indigenous flock.

Results

Phylogenetic analysis was performed on a part (498 bp) of the B2L gene of 35 Parapoxvirus isolates, including the two Orf virus isolates recovered from each of the two outbreaks in the present study. This analysis revealed that the maximum nucleotide and amino-acid variation amongst Orf virus strains worldwide (n = 33) was 8.1% and 9.6%, respectively. The homology of the nucleotide and amino-acid sequences between the two Greek isolates was 99.0% and 98.8%, respectively. The two Greek isolates clustered only with Orf virus strains.

Conclusions

We suggest that there can be differences between strains based on their geographical origin. However, differences in the origin of strains or in the clinical presentation of the disease may not be associated with their pathogenicity. More work is required to determine if differing clinical presentations are linked to viral strain differences or if other factors, e.g., flock immunity, method of exposure or genetic susceptibility, are more important to determine the clinical presentation of the infection.

Orf virus DNA vaccines expressing ORFV 011 and ORFV 059 chimeric protein enhances immunogenicity

Background

ORFV attenuated live vaccines have been the main prophylactic measure against contagious ecthyma in sheep and goats in the last decades, which play an important role in preventing the outbreak of the disease. However, the available vaccines do not induce lasting immunity in sheep and goats. On the other hand, variation in the terminal genome of Orf virus vaccine strains during cell culture adaptation may affect the efficacy of a vaccine. Currently, there are no more effective antiviral treatments available for contagious ecthyma.

Results

We constructed three eukaryotic expression vectors pcDNA3.1-ORFV011, pcDNA3.1-ORFV059 and pcDNA3.1-ORFV011/ORFV059 and tested their immunogenicity in mouse model. High level expression of the recombinant proteins ORFV011, ORFV059 and ORFV011/ORFV059 was confirmed by western blotting analysis and indirect fluorescence antibody (IFA) tests. The ORFV-specific antibody titers and serum IgG1/IgG2a titers, the proliferation of lymphocytes and ORFV-specific cytokines (IL-2, IL-4, IL-6, IFN-γ, and TNF-α) were examined to evaluate the immune responses of the vaccinated mice. We found that mice inoculated with pcDNA3.1-ORFV 011/ORFV059 had significantly stronger immunological responses than those inoculated with pcDNA3.1-ORFV011, pcDNA3.1-ORFV059, or pcDNA3.1-ORFV011 plus pcDNA3.1-ORFV059. Compared to other vaccine plasmids immunized groups, pcDNA3.1-ORFV011/ORFV059 immunized group enhances immunogenicity.

Conclusions

We concluded that DNA vaccine pcDNA3.1-ORFV011/ORFV059 expressing ORFV011 and ORFV059 chemeric-proteins can significantly improve the potency of DNA vaccination and could be served as more effective and safe approach for new vaccines against ORFV.